我自己找到了
DoEvents '
keybd_event 18, 0, 0, 0
keybd_event vbKeySnapshot, 0&, 0&, 0&
DoEvents
keybd_event 18, 0, KEYEVENTF_KEYUP, 0
CommonDialog1.Filter = "bmp文件|*.bmp|GIF文件|*.GIF|所有文件|*.*"
CommonDialog1.ShowSave
SavePicture Clipboard.GetData, CommonDialog1.FileName